1. Field of the Invention
The present invention relates to a display device, and more particularly, to an organic electroluminescence (EL) display device and a method for fabricating the same.
2. Discussion of the Related Art
A method of using a shadow mask as shown in FIG. 1 is the most efficient method to improve the luminescence efficiency among methods of forming R, G, and B pixels in fabricating a full-color organic EL display device.
FIGS. 1A to 1D are diagrams showing a related art shadow mask and a full-color organic EL display device according to a pixel array method.
As shown in FIG. 1A, an first electrode 2 is formed on a transparent substrate 1 and barriers 7 are additionally formed on the same to separate between an insulating film 3 and a second electrode.
Also, using a shadow mask 6, a common luminescence layer 5 of R, G, and B, and each of organic luminescence layers 5-1 to 5-3 of R, G, and B is formed at a corresponding pixel on the insulating film 3.
Then, the second electrode is formed on the entire surface.
There are three different types (i.e. a strip type as shown in FIG. 1B, a delta type as shown in FIG. 1C, and an array type as shown in FIG. 1D) in forming an organic luminescence layer using a shadow mask depending on the array method of a pixel. In the array type, the size of R pixel is designed to be larger than G or B pixel to supplement the luminescence efficiency of the R pixel.
The strip type is best among the above three pixel array types in terms of the aperture ratio and first electrode resistance. In other words, because first electrodes are formed in the form of strips, the device can be driven with low driving voltage.
On the other hand, in the strip type, the shadow mask 6 should also be made in a strip form as shown in FIG. 1. In this instance, problems such as the transformation or droop of the shadow mask 6 are caused in a large degree because of an external pulling strength. Accordingly, in the process of deposition, colors spread not only on the intended pixel region but also on other areas because of shadow effect.
To obviate the above-mentioned problems, as shown in FIG. 2, a shadow mask on which mask holes are made in turns while having the same pixel array structure as that of the strip type of FIG. 1B is applied.
FIGS. 2A to 2D are deposition process diagrams of an organic luminescence layer of a full-color organic EL display device using the related art shadow mask structure.
In this method, however, each organic luminescence layer displaying one of R, G, and B colors should be formed by carrying out alignment and deposition twice respectively. That is, to form three layers of R, G, and B, the deposition should be carried out six times in all after the alignment being carried out six times as well.
In other words, to form organic luminescence layers of R, G, and B, in case of using the shadow mask 6 of FIGS. 1B to 1D, the shadow mask is aligned and deposited three times respectively. In case of using a shadow mask shown in FIG. 2, however, the shadow mask should be deposited 6 times.